It is very easy to build an Inverted Vee Antenna to get on the air with your new Ham Radio Station. The Inverted Vee is the most popular antenna used by Ham Radio Operators. I suppose that’s because it’s very inexpensive and requires very little time to put up in the air. All you need is wire (about 12 to 16 gauge stranded or solid with or without the insulation), 3 insulators, some chord to tied off the ends and to hold the center insulator and the coaxial feed line. RG58 will do very well for feed lines of short length of less than 100 feet at the lower Ham Radio Frequencies and for power levels about 100 watts. RG8X is a little better because it will have less signal loss on the higher frequencies. For high power transmitters and/or mush less signal loss buy either RG213 or LMR-400 coax.
Below is a chart of over-all lengths of your antenna for the various bands. If you remember on your Ham Radio License test, the formula is 468/frequency in megahertz. The lower bands such as 160, 75/80 and 40 meters will be rather narrow banded in resonant frequencies. In other words, you can only safely operate about 20KHz around the center frequency of your antenna.
|Band||CW (Code) Length “A”||SSB (Voice) Length “A”|
|160 meters||246′-4″ center of band|
|30 meters||46′-2″ for entire band|
|17 meters||25′-9″ for entire band|
|12 meters||18′-9″ for entire band|
|10 meters||16′-6″ CW & SSB||15′-10″ FM|
Begin by determining which band you might use most often. If you plan on operating at night then the 160 through 30 meter bands would give you more stations to operate. If you plan on operating more during daylight hours then the 30 through 10 meter bands would give you more stations to operate. However, during periods of low sun spot activity, the daylight or higher bands will only have short sporadic openings. 30 meters seem to have the same qualities of both the higher bands and the lower bands. Also consider how much real estate you have for an antenna. Many city dwellers find it difficult installing a full size 75/80 meter (or larger) antenna because of the large amount of space required.
Measure off a length of wire according to the chart above plus about 12″ more for the amount needed to attach the insulators. Fold this length of wire in two and cut at the center. This is where we will attach a center insulator. Strip off about 3 inches of wire, feed it through the ends of the insulator, twist and solder to secure it. Do the same to the opposite outer ends and solder to the other two insulators. Opposite the end insulators you can use more wire or I like to use chord to support the ends to something about 6 feet above ground like a tree limb or a fence post. You now have your half wave antenna and you need to connect the coaxial feed line.
Figure about how much coax you will need to go from the top of your support and to your operating location, then add about 3 more feet for the coax loop RF choke. On the antenna end roll the coax into 6 turns about 6 to 8 inches in diameter. Secure the loops with electrical tape. This creates a RF choke to prevent the coax from radiating as part of the antenna. Leave about 4 inches straight and strip the coax down exposing the center conductor and exterior braid. Keep this part as short as physically possible. Now solder the center conductor to one side of the center insulator and then solder the braid to the other side. I like to use liquid electrical tape (available from Home Depot) and coat the exposed wires to prevent rain water from contaminating the coax. You do not want moisture from seeping into the coax for that will cause problems in time. Don’t use a silicon cement because that kind of cement has a corrosive effect on copper parts. Now tie a non-conductive chord to the center insulator so to hoist it up on your support.
Antenna Support – This will be the hard part. It is recommended to have the center feed point as high as possible or at least 1/4 wave length above ground. 1/4 wave length is a little longer than one half of the over-all length of your antenna. For example, a 40 meter antenna is best if the center feed point is about 36′ above ground. If you can’t get the antenna 1/4 wave length up in the air don’t worry too much about it. Your angle of radiation might be a little higher than you want and/or it could effect the impedance of the antenna a little. Many Hams might use a push-up TV antenna mast available from various sources. If you have a two storey home you can attach your antenna support to a part of your house. Be vary careful of nearby power lines. If you don’t get killed you could pick up unwanted electrical noise from those power lines. Just stir very clear of power lines. Also, try to stir clear of trees. Trees can attenuate your signal some.
Now feed the radio end of the coax into the house to your operating position. Attach a PL-259 connector to the coax. A very useful piece of test equipment Hams keep in their shack is a SWR bridge often just called a SWR meter. An inexpensive one can be purchased from Radio Shack that is acceptable for frequencies below 30 megahertz. It’s not known for it’s great accuracy but if funds are scarce, it will do for now. If you’re rich, buy you an antenna analyzer such as the MFJ-259B or the MFJ-269B. This is a very useful tool that you can also use on your 2 meter mobile antenna.
Check the SWR of your new Inverted Vee antenna. If you can reduce the output power on your transceiver to a minimum amount such as 5 watts do so. Follow the instructions of your SWR meter and check for how much reflected power you might have. Is is generally accepted to not have a SWR higher than 1.8:1. If the SWR is up above 2:1 you can change the angle of the Inverted Vee and that will adjust the impedance and effect the SWR. You can also lengthen the legs of the antenna to lower the center frequency or shorten the legs of the antenna to raise the center frequency.
Multi Band antenna? Yes, you can interlace 2 antennas on the single feed point but try to keep the 2 antennas perpendicular to each other.
Congratulations! You’re on the air. I hope to see you in the pile-ups soon.